Senators on both sides of the aisle criticized Credit Suisse at a hearing on Wednesday, saying it helped thousands of Americans hide billions of dollars in assets from United States tax authorities.

“We’re interested in collecting taxes that we’re owed, that were evaded,” said Senator Carl Levin, the Michigan Democrat who heads the Permanent Subcommittee on Investigations. “We simply have got to use our own domestic laws to force cooperation from the banks.”

The hearing was the result of a two-year investigation into practices at the bank from 2001 through 2008, when, Senate investigators said, Credit Suisse bankers actively recruited American clients and helped them hide money offshore.

Brady W. Dougan, the chief executive of Credit Suisse, based in Zurich, said that only a small number of employees were involved in such activity and that the bank had moved decisively to improve compliance in the last five years.

“Some Swiss-based private bankers went to great lengths to disguise their bad conduct from Credit Suisse executive management,” Mr. Dougan told the panel. “While that employee misconduct violated our policies and was unknown to our executive management, we accept responsibility for and deeply regret these employees’ actions.”

But that apology did little to appease the committee, whose members expressed doubt that executives did not know that the bank was helping its American customers evade taxes, and anger that no employees had been fired for misconduct.

“If you believe that, I have some beachfront property in Arizona I’d like you to look at,” said Senator John McCain of Arizona, the ranking Republican member on the committee, briefing reporters in advance of the hearing.

The Senate investigation found that Credit Suisse held as many as 22,000 American accounts with assets worth an estimated $10 billion to $12 billion. Thus far, the identities of about 1 percent of account holders have been revealed to American authorities, though Credit Suisse has closed most of those accounts.

“We’re really talking about a minuscule number of individuals who have intentionally evaded U.S. taxes” that have been uncovered, Mr. McCain said at the hearing.

The Credit Suisse executives — generally deferential in the face of hours of barbed questioning — said that the bank had to comply with American and Swiss laws, which can be at odds on the issue of client privacy.

“We do not want U.S. clients who are not fully compliant with the laws of this country,” said Hans-Ulrich Meister, the head of Credit Suisse’s private banking and wealth management.

The bank executives repeatedly said that Swiss law prevented them from disclosing certain client information. In part, that is because the Senate has not ratified a bilateral treaty with Switzerland that would allow fuller disclosures.

“We are prepared to provide any information that we can legally provide,” Mr. Dougan said. “To break the law in one jurisdiction to provide that information is difficult for us to do.”

Mr. Levin told the executives, “You folks have not been willing to give us more than 238 accounts.” He then recounted the ways that the bank helped Americans hide assets and evade taxes, and added, “The jig is up.”

A 176-page report by the Senate committee said that the bank was going to great lengths to help Americans evade taxes. That included helping clients set up shell corporations, having Swiss bankers travel to the United States to avoid creating a paper trail and recruiting Americans at a New York “ball” and a golf tournament.

The report describes one instance in which a Credit Suisse banker “traveled to the United States to meet with the customer at the Mandarin Oriental Hotel and, over breakfast, handed the customer bank statements hidden in a Sports Illustrated magazine.”

It also described Credit Suisse opening an office at a Swiss airport. “It was an office of convenience for clients,” Mr. Dougan said, adding that it was used by account holders headed to and from Swiss ski resorts.

“It certainly was,” Mr. McCain retorted.

The Justice Department also came in for criticism; senators said it dragged its feet in prosecuting or settling with Swiss banks under investigation — an accusation that American law enforcement has strongly denied.

“The department is committed to global enforcement against financial institutions that engage in or facilitate cross-border tax evasion,” James M. Cole and Kathryn Keneally of the Justice Department said in prepared testimony to the committee. “We also continue to track down and hold accountable individuals who sought to evade their tax and reporting obligations by hiding money in foreign accounts.”

The Justice Department has said that it is investigating more than a dozen Swiss financial institutions. Banks, including Credit Suisse, have warned that continuing legal costs may take a toll on their bottom lines. Five years ago, UBS, the largest Swiss bank, admitted to helping American account holders avoid taxes.

A version of this article appears in print on 02/27/2014, on page B3 of the NewYork edition with the headline: Credit Suisse Executives Face Bipartisan Glare in Senate.